Macedonian Prime Minister Zoran Zaev and his Bulgarian counterpart, Boyko Borissov, will sign a historic friendship treaty in the Macedonian capital of Skopje on Tuesday that aims to leave behind historic differences aside and focus on future cooperation.

The occasion, deemed historic by observers in both countries, will be accompanied by much symbolism as well.

In Skopje, Borissov and Zaev will lay flowers at the tomb of the Ottoman-era revolutionary Goce Delcev, a historic figure that both countries revere as a national hero.

Amid criticism from opposition parties, Zaev last week insisted that the treaty would not harm or undermine Macedonia in any way but would, on the contrary, make Bulgaria “more dedicated” to friendship.

In his address to the Bulgarian parliament last week, Borissov insisted that the treaty would help make Macedonia a prosperous ally with which Bulgaria would eventually share common EU and NATO values.

Macedonia and Bulgaria share linguistic and cultural similarities but also hold differing views on their history and language, dating back to the 19th century, when Bulgarian nationalists claimed Ottoman-ruled Macedonia as part of Bulgarian territory.

Differences dating from those times have continued to impede relations. Bulgaria no longer claims Macedonia as "terra irredenta" but it still does not recognize the Macedonian language, which Bulgarian scholars view it as a dialect of Bulgarian.

The countries’ historical records also still differ over whether the Ottoman-era revolutionaries that both countries celebrate as national heroes were Bulgarian or Macedonian.

Each country has in the past accused the other of not respecting the rights of its national minority living across the border.

The treaty aims to put these various differences aside, acknowledging their shared history but also the right to hold different views on some topics.

The problem with the language is circumvented in the treaty with the help of some carefully balanced phrases.

The document states that the treaty is signed "in the Macedonian language according to the Macedonian constitution and in the Bulgarian language according to the Bulgarian constitution", for example.

Both countries will also now say they have no territorial claims against each other. Both countries also pledge to protect the rights of the other country's nationals living on their soil – not to interfere in the other's domestic affairs.

They both pledge to abide by international standards when it comes to respect for human rights.

In Macedonia, the strongest objections came from the former ruling VMRO DPMNE party, which said it will not support it in parliament.

For most observers, however, the agreement is a welcome historic step towards warmer bilateral relations.

"This is a big step, which heralds a new page in relations with our neighbour," Macedonian diplomat and former ambassador Ljupco Arsovski said.

"The treaty is not ideal. There is certainly a need for certain improvements, but it will serve well as a basic framework for future upgrades," Arsovski said.

The treaty puts a focus on cooperation in the fields of economy, infrastructure and culture, envisaging the formation of a joint work group that will meet at least once a year to discuss ways to improve cooperation.

For its part, Bulgaria has promised to wholeheartedly support Macedonia's aspirations to join NATO and the EU.

Skopje hopes that Sofia will be a staunch advocate for Macedonia when Bulgaria assumes the Presidency of the Council of the EU in January 2018.

The announced signing of the treaty has been welcomed both by Washington and Brussels.